Manufacture of steel dies.



CHARLES BALL AND HAROLD E. NOCK, OF PROVIDENCE, RHODE ISLAND, ASSIGNORS TO CLAUDE C. BALL, OF PROVIDENCE, RIIODE ISLAND.

MANUFACTURE OF STEEL DIES.

SPECIFICATION forming part of Letters Patent N 0. 722,351, dated March 10, 1903.

Application filed June 24:, 1902.

To all whom/it may concern:

Be it known that we, CHARLES BALL and HAROLD E. Noox, citizens of the United States, residing at Providence, in the county of Providence and State of Rhode Island, have invented certain new and useful Improvements in the Manufacture of Steel Dies, of

which the following is a specification.

Our invention relates to steel dies and their manufacture, and has for its purpose .the ends commonly sought--namely, the avoidance of expense in manufacture and the integrity and durability of the product.

The current methods of manufacture involve either cutting a design in a steel block or forcing a patrix into heated steel. coarse designs in soft metals, such as iron, the dies are cast in sand; but steel dies obviously cannot be thus cast. Attempts have been made to subject a block of heated steel to the stroke of a cast-iron patrix; but this requires too great an expenditure of expert labor to be commercially available. The use of bronze patrices upon a block of heated steel has been attempted, but results in welding the surfaces of the-patrix and die or when the steel is not at a high temperature defaces the patrix. Especially is this true in the case of dies, where the repetition of foreer-strokes gradually obliterates the outline of the figure on the die.

The disadvantages and obstacles above enumerated are obviated, as hereinafter set forth.

In changing from a molten to a solid state steel undergoes marked contraction, in which case the metal is radially dra wn' from the last place of solidification. When casting steel dies in open molds of high thermal conductivity, (such as iron,) the exterior of the casting contacting with the relatively cold mold is the first part to solidify and the upper surface the last, thus locating the center of shrinkage or cavity proximate the working face of the completed die, rendering the same unsound. Attempts have been made to overcome this difficulty by mechanically displacing the cavity by forcing a steel block into the cooling mass; but we control the location For Serial No. 112,979. (No model.)

of the inevitable cavity by subjecting the molten steel destined for the die to surroundings of varied degrees of conductivity.

Our improved process may be described in connection with the mechanism illustrated in the accompanying drawings, forming a part of this application, wherein- Figure 1 is a central transverse section of a mold and patrix, the latter provided with a flat workingfaoe; Fig. 2, a similar view of a modified form of mold and patrix-face, and

'Fig. 3 a like view of another modified form of mold and patrix.

Like letters of reference indicate like parts throughout the views.

A represents the upwardly-tapering walls of a rectangular mold, and B the base of the same, the whole composed of iron or steel possessing high thermal conductivity. Let into the base thereof is a layer C of non-conductible material, such as steel-crucible clay.

Leading to the upper portion of the central chamber D of the mold formed as above is the pouring-gate E. A large opening F in the top of the mold allows the ingress of the patrix G, carrying upon its lower surface the Working face H. The patrix is preferably of bronze composition of pronounced bulk and extensive area to speedily reduce the temperature of the molten mass of steel contiguous its face to a degree less than the meltingpoint of the patrix. The capacity of bronze to dissipate heat is very marked.

The modified form of mold and patrix working face shown in Fig. l is employed when the pronounced depth of the patrix contour threatens a too-sudden chilling of the lower center of the molten mass of steel from which the metal involved in shrinkage must be drawn. The same end is attained in molds of greater depth, as are sometimes required by the modified form of mold shown in Fig. 3, where in order to prevent an undue increase of conductive area the non-conductible layer D is extended upwardly from the mold-base some distance in the walls A of themold.

Our process may be described in connection with the molds above illustrated, as follows: The face H of the patrix G is polished with dry plumbago. The mold is then raised to a temperature approximating 300 or 400 Fahrenheit. The steel to be transformed into a die J is after melting poured through the pouring-gate E into and filling the chamher D. The exposed mouth of the pouringgate is covered in any convenient manner with a block of cold iron I, which immediately chills the contents of the gate. The patrix G is then forced through the opening F until the face H enters the molten steel J, deposited through the pouring-gate into the central chamber D. After restingin the mold a sufiicient time to solidify the mass of steel is removed from the chamber D and successively annealed, hardened, and tempered.

By our process it will be observed that at the instant the patrix-face enters the mobile steel mass J the steel conforms to the finest lines in the patrix-face, and the intimate contact of the steel with the cold and highlyconductible patrix above described solidifies the former and fixes a perfect impression of patrix. The physical action within the molten mass of steel J is as follows: The broad surface of the bronze patrix-face being the best thermal conductor insures a cooling of the upper surface of the mass J first. The conductivity of the surrounding walls A of steel or cast-iron being less than that of the bronze patrix cooling at points contiguous thereto is delayed somewhat, while the clay strip 0 in the mold-bottom, being an excessively poor thermal conductor, insures the last place of cooling of the die J to be at a point K at or near the clay bottom and equidistant from the sides of the die. In the drawings the lines converging from the surface of the die J toward the point K indicate the lines of contraction or crystallization. This formation gives to this cast die a strength which compensates for the absence of a fibrous formation, which is the peculiar feature of forged steel, and directs the strain upon the die involved in its use along these lines of contraction to the base of the die, where its increased mass is adapted to receive the greatest strain without injury.

Having described our invention, what We claim as new, and desire to secure by Letters Patent, is'

1. The process of making solid steel dies which consists in inclosing a molten mass of steel within a chamber, fixing the last point of solidification of the entire mass while cooling at a point nearer the base than the top of the cooling mass, and finally annealing, hardening, and tempering the same.

2. The process of making steel dies which consists in inclosing a molten mass of steel within a chamber, impressing a patriX-face in the upper surface of said mass while the latter is in a plastic condition, fixing the last point of solidification of the entire mass while cooling at a point nearer the base than the top of the cooling mass, and finally annealing, hardening, and tempering the same.

3. The process of making steel dies which consists in inclosing a molten mass of steel within a chamber, impressing a patrix-face of bronze composition in the upper surface of said mass while the latter is in a plastic condition, fixing the last point of solidification of the entire mass while cooling at a point nearer the base than the top of the cooling mass, and finally annealing, hardening and tempering the same.

4. The process of making steel dies which consists in inclosing a mass of molten steel within a chamber, impressing a patrix-face in the upper surface of said mass, retarding the radiation of heat from the bottom of the mass during the period of cooling, and finally annealing, hardening, and tempering the same.

5. The process of making steel dies which consists in reducing the steel to be converted into a die to a molten mass by any convenient means, exposingthe upper surface thereof to a metallic surface of great thermal conductivity, contemporaneously subjecting the sides of the same to a surface of less conductivity than the first contacting surface, simultaneously subjecting the bottom of said mass to a surface of non-conductible material, and finally annealing, hardening and tempering the mass thus treated.

6. The process of making steel dies which consists in reducing the steel to be converted into a die to a molten mass by any convenient means, impressing a patrix-face composed of metal of great thermal conductivity, into the mass previous to solidification, contemporaneously subjecting the sides of the cooling mass to a surface of less conductivity than that of the patrix-face, simultaneously subjecting the bottom of said mass to surface of non-conductible material, and finally annealing, hardening and tempering the mass thus treated.

7. The process of making steel dies which consists in reducing the steel to be converted into a die to a molten mass by any convenient means, impressing a patrix-face of bronze composition into the upper surface of the mass previous to solidification, exposing the sides of the cooling mass to iron or steel, walls previously heated to about 200 Fahrenheit, simultaneously exposing the bottom of the mass to a layer of clay, and finally annealing, hardening and tempering the mass thus treated.

8. The process of making steel dies which consists in pouring melted steel into a mold in which areas of differing thermal conductivity are variably arranged to control the physical conditions incidental to the solidification of the steel, impressing a patrix-face in the surface of the steel before its solidification, and finally annealing, hardening and tempering the material thus treated.

9. As a new article of manufacture, a die consisting of a single block of steel, a figure IIO impressed in the top thereof, and a center of shrinkage nearer the bottom than the top of the block.

10. As a new article of manufacture, a die consisting of a single block of steel, a figure In testimony whereof we have affixed our signatures in presence of two witnesses. CHARLES BALL. HAROLD E. NOOK.

Witnesses:

impressed in the top thereof, and a center of HORATIO E. BELLOWS, shrinkage adjacent the bottom of the block. ROBERT L. STANTON. 

